1. Field of the Invention
The present invention relates to a method of delivering difference map data in which, upon updating map data via a network in a navigation system, updated portions of the map data are delivered and displayed.
2. Description of the Related Art
Map data, including data on roads, facilities, etc., are stored in car navigation devices installed in vehicles. A car navigation device uses these map data to realize functions of displaying a map of the surroundings of the vehicle position, etc., on a screen and searching for routes to destinations and waypoints indicated by a user. The map data stored in a car navigation device are thus preferably updated constantly to the newest data. However, updating of all of the map data stored at one point in a batch at once will take up considerable amounts of money and time and is not necessarily beneficial to a user.
The updating of just difference data, which, among the map data of the car navigation device, are necessary at one time, has thus been proposed. For example, Japanese Published Unexamined Patent Application No. 2004-37331 (paragraphs 0032 to 0039, FIG. 3 and FIG. 4) discloses a map data delivering system that displays area information corresponding to a predetermined range in the vicinity of a position specified by position data of a vehicle and whereby a user selects, from the area information, an area for which the user desires the delivery of data. Also, Japanese Published Unexamined Patent Application No. 2002-342330 (paragraphs 0048 to 0062, FIGS. 3, 6, and 7) discloses a navigation device that displays a menu screen for downloading the newest map data and whereby a user selects, in accordance with the screen, an area or POI (Point of Interest; a sightseeing spot or any of various facilities) genre for which the user wishes to download data.
However, with the conventional car navigation devices, prior to the downloading of map data, a user knows only the information that data of a predetermined area are going to be updated and does not know what actually in that area will be new or will change (that is, a user cannot preview the update data). The user thus is not sure of the cost and time it takes to download the map data and may feel insecure.